Figure 5.
Circulating plasmablasts (PBs) induced by H7N7 inactivated influenza vaccination in H7N7 live attenuated influenza vaccine (LAIV)–primed and unprimed cohorts. Peripheral blood mononuclear cells (PBMCs) collected on day 7 after the inactivated vaccine were analyzed by an enzyme-linked immunospot assay for immunoglobulin G (IgG)–secreting PBs. PB specificity was assessed against H7 from NL/00, NL/03, AN/13, and BC/04; H7 head only from SH/13; chimeric cH4/7; and H1 from CA/09. Frequencies are shown for individual subjects (n = 7 for each cohort), together with the geometric mean titer (GMT). PBs specific for antigens in the panel were not detected in PBMCs obtained on day 0 from any subject (frequencies < 1/106 PBMCs). Differences between cohorts in specific PB frequencies were examined by 2-sample t tests, using data on a log scale. P values are only shown for comparisons that were significantly different (P < .05).